System and method for imaging in laser dental treatment

ABSTRACT

A device for determining a contour of a dental treatment area during treatment thereof includes a laser beam guidance system and an imaging system. The laser beam guidance system can guide a laser beam and, optionally, a scanning light to a dental treatment area, and the imaging system, which can include an adjustable focus image sensor, can obtain an image of the dental treatment area based on light rays reflected therefrom. The device also includes a computation system to compute a contour, e.g., a 2D contour, of a surface of the dental treatment area based on the image obtained by the imaging system and, optionally, geometries of one or more components of the laser beam guidance system and/or optical components associated with the imaging system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of priority to U.S. Provisional PatentApplication No. 61/793,117, entitled “System and Method for Imaging inLaser Dental Treatment,” filed on Mar. 15, 2013, the disclosure of whichis incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention generally relates to three dimensional (3D)scanning and, in particular, to generating a model of unevenly shapedobjects such as dental structures.

BACKGROUND

In dentistry, 3D scanning and imaging are rapidly replacing oldertechniques that use castings and impression materials. Scanning istypically fast relative to the older methods, can instantly provide adigital file, and can eliminate substantially all shrinkage and handlingissues associated with castings and impressions. Additionally, thedigital images can be easily transmitted to a dental laboratory ordental computerized numerical control (CNC) milling machine, forgenerating a suitable dental restoration component such as a dentalcrown.

Scanners, in general, are devices for capturing and recordinginformation from the surface of an object. The use of scanners todetermine a 3D surface contour of an object , e.g., to create a 3D modelthereof, using non-contact optical methods is important in manyapplications including in vivo scanning of dental structures. Typically,a 3D surface contour is formed from a collection of points (often calleda cloud of points) where, at a particular time, the relative position ofeach point in the collection/cloud represents an approximate contour ofthe scanned object's surface.

In these optical methods, a common principle underlying contourmeasurement using the collection of point position data istriangulation. Given one or more triangles where the baseline of eachtriangle includes two optical centers and the vertex of each triangle isa particular point on or near a target object surface, the range of thatparticular point on or near the target object surface from each of theoptical centers can be determined based on the optical separation andthe angle of light transmitted from and/or received at the opticalcenters to/from the particular point. If the coordinate positions of theoptical centers in a specified coordinate reference frame (e.g., aCartesian X, Y, Z reference frame), are known, the relative X, Y, Zcoordinate position of the vertex, i.e., the point on or near the targetsurface, can be computed in the same reference frame. Typically, thelight rays from an illumination source to a point on the target form oneleg, i.e., edge, of the triangle, and the rays reflected from the targetpoint to an image sensor form the other leg, i.e., edge, of thetriangle. In a system using a single image sensor, the angle between thetwo legs can be determined because the positions of the illuminationsource and the sensor and the angle at which a beam of illuminationlight is directed to the surface to be scanned are known. Using theseknown parameters and the computed angle of reflection, the expectedposition of the point of reflection on the surface to be contoured canbe determined. By repeating this procedure to determine the respectivepositions of a number of points of reflection a curvature of thereflection surface, i.e., the 3D contour thereof, can be determined.

Triangulation methods can be divided into passive triangulation andactive triangulation. Passive triangulation (also known as stereoanalysis) typically utilizes ambient light and the two optical centersalong the baseline of the triangle include two cameras/image sensors. Intwo sensor passive systems, knowledge of the angle of illumination lightincident upon the object to be scanned is not required. In contrast,active triangulation typically uses one camera as one optical center ofthe triangle along the baseline and, instead of a second camera at theother optical center, active triangulation uses a source of controlledillumination (also known as structured light). One optical center is asource of light and the other optical center is the imaging device, asdescribed above.

Stereo/passive analysis, while conceptually straightforward, is notwidely used, e.g., due to the difficulty in obtaining correspondencebetween features observed in different camera images. The surfacecontour of objects with well-defined edges and corners, such as blocks,can be relatively easy to measure using stereo analysis. Objects thathave smoothly varying surfaces, such as skin, tooth surfaces, etc., haverelatively fewer easily identifiable points of interest, such ascorners, edge points, etc. This can present a significant challenge tothe stereo analysis techniques. Active triangulation is therefore oftenpreferred in generating 3D contours of such objects having smoothlyvarying surfaces.

Active triangulation, or structured light methods, can overcome or atleast minimize the stereo correspondence problems by projecting one ormore known patterns of light onto an object to determine the shapethereof. An example structured light is a spot of light, typicallyproduced by a laser. Accuracy of contour determination can be increasedby moving a fine spot in a specified pattern, e.g., along a line, in azig-zag pattern, and/or a spiral pattern. One large spot can also beused, however. The geometry of the setup of the light projector and thecamera observing the spot of light reflected from a surface of thetarget object can enable, e.g., via trigonometric calculations, thedetermination of a range of the point from which the light spot isreflected from one or both optical centers (i.e., the light projectorand camera), as described above. Light projection patterns such as astripe or two-dimensional patterns such as a grid of light dots can beused to decrease the time required to capture and/or analyze the imagesof the target surface.

The resolution of the measurement of the surface of a target objectusing structured light generally depends on the fineness of the lightpattern used and the resolution of the camera used to observe thereflected light. Typically, the overall accuracy of a 3D lasertriangulation scanning system is based on the ability thereof to meettwo objectives, namely: (i) accurately measuring the center of theillumination light reflected from the target surface, and (ii)accurately measuring the position of the illumination source and thecamera at each of the positions used by the scanner to acquire an image.

Commercially available 3D scanner systems have been developed for thedental market that accommodate the variety of human dentitions byincorporating an operator held, wand type scanner. In these systems, theoperator typically moves the scanner over the area to be scanned andcollects a series of image frames. In this case, however, a positionalcorrespondence between image frames is typically not maintained; insteadeach frame is captured from an unknown coordinate position that isindependent of the position and orientation of the wand at the instantthe previous one or more frames of images were captured. In addition,all orientation information about the illumination sources and imagingdevices and references thereto from scanning prior to treatment aregenerally not available to a scan after the treatment, because thescanner cannot be continuously located in the mouth during treatmentwith other instrumentation used for treatment.

These handheld systems must therefore rely on scene registration or theapplication of an accurate set of fiducials over the area to be scanned.But, for 3D structures such as teeth, the use of pattern recognition orfiducials for frame registration can be error prone, because toothsurfaces do not always provide sufficient registration features to allowfor high accuracy scene registration. Accurate placement of fiducials toa resolution that is often required is generally impractical over thesize of a typical tooth.

Another 3D measurement method includes auto-focus depth measurement withimage recognition. With a short depth of field, the camera is focused atpredefined depth (e.g., Z1), and an image is captured. The image is thenprocessed, e.g., using an image recognition software, so that the“in-focus” sections of the image can be determined. Another image isthen captured at a second predefined depth (e.g., Z2), and the“in-focus” sections in the second image are identified. The Z depthpositioning, image capture, and image recognition are repeated accordingto a required resolution. Once all of the images are captured, theindividual image slices can be stacked together to create a 3D image ofthe object.

In connection with scanning and modeling a treatment area, this methodoften produces 3D scans lacking the required level of accuracy. This islargely because the images are captured before and after the treatmentonly, and no images are captured during treatment because that requiresinterchanging treatment and imaging devices, which cause delay intreatment, inconvenience to the patient, and may also pose safety riskto all those involved in the treatment, particularly when lasers areused in the treatment. Therefore, improved systems and methods are needfor scanning areas/regions to be treated.

SUMMARY OF THE INVENTION

In order to improve the quality of conventional 3D measurement duringhard tissue cutting, various embodiments of a laser cutting systemintegrate an optical scanning and measurement system and a laser-basedablation system. The scanner can include an active triangulationmeasurement technology, or in-focus image recognition technology, orboth. Unlike the conventional systems, however, various embodiments ofthe integrated system enable reconstruction of a 3D image of the removedtissue using a number of essentially two-dimensional (2D) images and 2Dcontours based on those 2D images. The 2D images and contours cancorrespond to thin slices of the tissue, i.e., a slice thickness can be,for example, about 0.02 mm, 0.05 mm, 0.1 mm, 0.5 mm, etc. Various 2Dimages and the contours generated therefrom correspond to images takenduring treatment, so as to provide an accurate 3D model of the tissuethat is removed during treatment.

Conventional scanners and laser-based treatment systems typicallyinclude optical components that are not compatible with each other. Assuch, these two types of systems cannot be readily combined. Tofacilitate integration of a scanning system and a treatment system, invarious embodiments at least some components of the optical subsystemfor laser delivery (also called a beam-guidance subsystem) are adaptedto perform at least some of the scanning/measurement functions, as well.Additionally, or in the alternative, some components of thescanning/measurement system may be positioned at selected locations andorientations relative to the components of the beam-guidance system suchthat the combined geometries of the two subsystems can be used in thecomputation of surface contours, while minimizing any interference ofthe components of the scanning system with the delivery of the laserbeam.

Accordingly, in one aspect, a device for determining a contour of adental treatment area includes a laser beam guidance system and at leastone imaging system. The laser beam guidance system can guide a laserbeam via a hand piece to a dental treatment area. The imaging system canobtain an image of the dental treatment area based on light raysreflected therefrom and traveling via the hand piece. The device alsoincludes a computation system adapted for determining, based on theimage obtained by the imaging system, a contour of a surface of thedental treatment area. The computations may be based on geometries ofone or more components of the laser beam guidance system and/or opticalcomponents associated with the imaging system. The device may includetwo or more imaging systems.

In some embodiments, the imaging system includes an adjustable focuslens. The device may also include a joystick and/or a foot pedal foradjusting a focal length of the adjustable focus lens. The adjustablefocus lens may include one or more of a motorized lens stack and aliquid lens. The imaging system in its entirety or some componentsthereof may be located within the hand piece. The computation system maybe adapted for determining an in-focus portion of the image.Alternatively, the computation system may be adapted for determining thecontour based at least in part on a geometry of a component of the laserbeam guidance system and/or a geometry of a component of the imagingsystem.

In some embodiments, both the laser beam and the light rays reflectedfrom the dental treatment area, that are received by an imaging system,travel along a common optical axis. The device may include a splitterfor directing the light rays reflected from the dental treatment area tothe imaging system, instead of directing such rays to the laser source.In some embodiments, the laser beam is guided to the dental treatmentarea along a first axis and light rays reflected from the dentaltreatment area, that are received by an imaging system, travel along asecond axis that is at an angle with respect to the first axis. Thedevice may include two or more imaging systems. One imaging system mayreceive light traveling along the common optical axis and anotherimaging system may receive light traveling along the second axis. Insome embodiments, one imaging system may receive light traveling alongthe second axis and another imaging system may receive light travelingalong a different, third axis, that is also at an angle relative to thefirst axis.

The device may include an illumination system for providing light to thedental treatment area. The illumination system may be adapted forproviding light having a pattern, and the pattern may include one ormore of a spot, a one-dimensional pattern, and a two-dimensionalpattern. In some embodiments, the laser beam guidance system is adaptedto scan the dental treatment area by directing light from theillumination system, e.g., according to a specified pattern and/or witha specified shape.

In another aspect, a method of determining a contour of a dentaltreatment area includes (a) receiving at an imaging system a first imagebased on a first set of light rays reflected from a dental treatmentarea and traveling via a hand piece, and (b) generating a first contourof the dental treatment area based on the first image. The method alsoincludes (c) directing via the hand piece a laser beam to the dentaltreatment area, e.g., using a laser beam guidance system. At least aportion of tissue from the dental treatment area may be removed as aresult of directing the laser beam. The method further includes (d)receiving at the imaging system a second image based on a second set oflight rays reflected from the dental treatment area and traveling viathe hand piece, and (e) generating a second contour of the dentaltreatment area based on the second image. The steps (c) through (e) maybe repeated, alternating between imaging and ablation, until treatmentis completed. The first contour and/or the second contour may include atwo-dimensional (2D) contour.

In some embodiments, receiving the first image includes adjusting afocal length associated with the imaging system, and generating thefirst contour includes determining an in-focus portion of the firstimage. The focal length may be adjusted using a joy stick and/or a footpedal. In some embodiments, both the laser beam and the first and secondsets of light rays reflected from the dental treatment area and receivedby the imaging system travel along a common optical axis.

In some embodiments, receiving the first image includes scanning thedental treatment area according to a pattern of light obtained from anillumination system. The laser beam may be guided to the dentaltreatment area along a first axis and the first and second sets of lightrays reflected from the dental treatment area and received by theimaging system may travel along a second axis that is at an angle withrespect to the first axis. The pattern of the illumination light mayinclude a spot, a one-dimensional pattern, and/or a two-dimensionalpattern. In some embodiments, the laser beam guidance system iscontrolled so as to scan the dental treatment area according to thepattern of light.

In some embodiments, the method included using the 2D contours togenerate a three dimensional (3D) model of portions of tissue removedfrom the dental treatment area. The method may further include creatinga restoration using the 3D model. As the 2D contours are determined fromtissue scans that are interleaved between different treatment steps, andbecause the system can estimate the depth of tissue removed in each ofthose treatment steps according to the system parameters, thereconstruction of the 3D model can be based on the estimated depthcorresponding to each one of the 2D contours, thereby increasing theaccuracy of the 3D model. The 3D model may be modified prior to creatingthe restoration. The method may also include applying the restoration tothe dental treatment area.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more apparent in view of the attacheddrawings and accompanying detailed description. The embodiments depictedtherein are provided by way of example, not by way of limitation,wherein like reference numerals generally refer to the same or similarelements. In different drawings, the same or similar elements may bereferenced using different reference numerals. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingaspects of the invention. In the drawings:

FIG. 1 depicts an overall laser-based system adapted for both treatmentand scanning the area to be treated, according to one embodiment;

FIGS. 2A-2C depict dental systems for scanning and treatment accordingto different embodiments;

FIG. 3 illustrates an exemplary alternate scanning and ablationprocedure in which scanning is performed using structured light,according to one embodiment;

FIG. 4 illustrates another exemplary alternate scanning and ablationprocedure in which scanning is performed using focus adjustment,according to one embodiment; and

FIG. 5 illustrates an exemplary alternate scanning and ablationprocedure to obtain a number of two-dimensional (2D) contours andreconstruction of a three-dimensional (3D) model based thereon,according to one embodiment.

DETAILED DESCRIPTION

With reference to FIG. 1, a laser source can direct a laser beam into anarticulating arm launch 1. The beam may be further directed within anarticulated arm 2, and may exit therefrom at the end opposite thelaunch. In this laser-based dental treatment system, a main chamber 3 isconnected to an interchangeable hand piece 4. One embodiment includes avariable speed foot pedal 6 to control the laser source and/or variousparameters of the dental system. A user interface (e.g., a touch screeninput device) and/or monitor 5 can display images, and may be used tocontrol various system parameters instead of or in addition to the footpedal 6.

With reference to FIG. 2A, in one embodiment, a main chamber 3 of adental laser system houses an X Galvo 9 and a Y Galvo 11, and associatedreflective mirrors 10, 12 that are mounted on the X and Y galvanometers,respectively. The laser beam enters the module approximately along axis8, reflects off the respective reflective mirrors 10, 12 of X Galvo 9and Y Galvo 11, is redirected through the hand piece 4 substantiallyalong axis 13, reflects off turning mirror 17, and exits the hand piecesubstantially along axis 18. In this embodiment, a camera assembly 30A,which includes an image sensor 22A, a filter 21A, a fluidic lens 20A, alens stack 19A, and a focusing motor 23A, is mounted within the mainchamber 3. The camera assembly 30A can receive a beam of light split bya beam splitter 25. The beam splitter 25 can transmit therethrough thetreatment laser beam and, optionally, a marking laser beam,substantially along the optical axis 13.

An optical device 14 can emit light from a light source 15 through alens 16, non-collinearly but in parallel to the optical axis 13. Theemitted light can reflect off the turning mirror 17, and may be emittedthrough the tip of the hand piece 4, with a waist around the opticalaxis 18, towards a treatment area. Alternatively, the illumination lightsource can be coupled into a light guide and be emitted towards theturning mirror 17 in a hand piece, so that the illumination light isdirected to the treatment area. Light reflected from the treatment arearepresenting a visible image thereof may propagate substantially alongthe hand piece axis 18, reflect off turning mirror 17, propagatesubstantially along the optical axis 13, and may be reflected off thebeam splitter 25 along an optical axis 24 into the image sensor 22A. Asthe laser beam and the light reflected from the treatment area bothtravel along the axis 13, the camera assembly 30A may be referred to as“on-axis” camera assembly.

In addition, a camera assembly 30B that includes an image sensor 22B isalso located in the hand piece 4, along with a filter 21B, a fluidiclens 20B, a lens stack 19B, and a focusing motor 23B. The image sensor22B can be mounted such that light reflected from the area of treatmententering the hand piece 4 along the optical axis 27 and reflecting off aturning mirror 26 can propagate along axis 35 to the image sensor 22B.In one embodiment, the optical axis 27 is at an angle of about 15°relative to the axis 18. In general, the angle between the two axes 18,27 can be within a range from about 5° up to about 45°. No significantportion of the light received at the camera assembly 30B travels alongany of the axes along which the laser beam propagates, e.g., the axes13, 18. Therefore, the camera assembly 30B may be referred to as“off-axis” camera assembly. In each camera assembly 30A, 30B, variouscomponents, namely, the filter, fluidic lens, lens stack, and focusingmotor are optional. Different embodiments of a camera assembly caninclude none, any one, or a combination of any two or more of thesecomponents.

Though FIG. 2A shows two camera assemblies 30A, 30B, i.e., imagingsystems, it should be understood that this is for illustrative purposesonly. Various embodiments may include only the camera assembly 30A oronly the camera assembly 30B. Some embodiments include two or moreoff-axis camera assemblies. For example, with reference to FIG. 2B, oneembodiment includes two off-axis camera assemblies 30B, 30C in additionto the on-axis cameral assembly 30A. With reference to FIG. 2C, anotherembodiment does not include the on-axis camera assembly 30A but includetwo off-axis camera assemblies 30B, 30C. More than two off-axis cameraassemblies may also be included. Each of the camera assemblies 30B, 30Cis positioned at different locations in the hand piece 4. Either or bothof these assemblies can also be located in the main chamber 3. Thecamera assembly 30B receives light reflected off mirror 26B, impingingthereon along axis 27B, and the camera assembly 30C receives lightreflected off mirror 26C, impinging thereon along axis 27C. The axes27B, 27C are at an angle relative to each other and are at differentangles, respectively, relative to the optical axis 18. In someembodiments, both off-axis camera assemblies 30B, 30C may receive lightreflected off one mirror, e.g., mirror 26B or mirror 26C, but impingingthereon along different axes that are at different angles relative toeach other and to the optical axis 18. The images obtained from two ormore camera assemblies can be analyzed to accurately determine the depthof the corresponding image slices.

FIG. 3 illustrates an exemplary treatment process in which ablation andmeasurement/scanning using structured light are performed alternately.The galvanometers 9 and 11 are housed in the main chamber 3 and candirect visible light for measurement (and far infrared light, e.g., alaser beam, for ablation), received along optical axis 8, towards thetissue to be treated. The visible light is reflected off thegalvanometer mirrors that are used to direct the ablation laser duringtreatment, and may propagate substantially along the optical axis 13,reflect off the turning mirror 17, and then exit the hand piece 4 alongthe optical axis 18. The hand piece 4 houses an image sensor 22B whichcan receive images of the tissue being treated. In particular, lightreflected from the tissue can enter the hand piece 4 along an opticalaxis 27, reflect off a tuning mirror 26, and can be received by thesensor 22B along the axis 35B, which is substantially parallel to theoptical axis 13. Step 1 illustrates a movement of the galvanometers 9,11 to direct visible light onto a tooth 28 in an ovular region 29. Asthe visible light is scanned by galvanometers 9, 11 the light reflectingfrom the tooth surface can be captured by the image sensor 22B, asdescribed above. Using the captured images, a contour of the scannedtooth surface can be determined.

Step 2 shows the ablation laser reflecting off the turning mirror 17,propagating along the optical axis 18, and ablating a portion of thetooth 28 in a pattern 30. Step 3 shows the structured (i.e., scanned)visible light being directed again to the tooth 28. In this step, thelaser system can be turned off so that the ablation laser beam is notdirected to the area to be treated. In step 3, the image sensor 22B canmeasure the contour of the treatment area, including the of the surfaceof the tooth 28, that was at least partially treated according to theablation pattern 30 after the ablation in step 2. Step 4 shows theablation laser being reactivated and ablating an additional portion ofthe tooth 28. In step 5, the ablation laser is turned off and a newmeasurement is obtained after the ablation in step 4. Ablation cancontinue in step 6 and, in general, the treatment process that includesalternating ablation/contour determination steps is continued until aselected treatment is completed.

In one embodiment, during scanning, the galvanometer mirrors may rotateinto a “park” position not used during laser ablation, and may flutter,i.e., move in a controlled manner. This can cause the structured lightto be directed to the dental treatment area within a selected shape(circle, oval, rectangle, etc.) according to a specified scanningpattern such as a zig-zag pattern, spiral pattern, etc., to scan thetreatment area (e.g., a surface of a tooth) with the controlledillumination.

FIG. 4 illustrates another embodiment of a treatment process thatincludes the alternating ablation and measurement steps, using focusadjustment and recognition for the optical measurements. Scanning is notrequired in an adjustable focal length system. In this embodiment,ablation is performed using a laser beam guided by galvanometers, andthe 2D measurement is performed using an “on-axis” camera withadjustable focus. On-axis generally means at least partial propagationof the light used to capture images and at least partial propagation ofthe light reflected from the treatment region that may represent animage thereof occur substantially along a common axis, e.g., the opticalaxis 13.

In step 1, an image sensor 22A can image the tooth 28 using lightreflected from a treatment area and received via an optical axis 18,reflected over the turning mirror 17, propagating substantially alongthe optical axis 13, and being redirected by the beam splitter 25substantially along the axis 24. Alternatively or in addition, in someembodiments, with reference to FIG. 3, the sensor 22B can image thetooth 28 using light reflected from a treatment area and received viathe optical axis 27, reflected over the turning mirror 26, andpropagating substantially along the optical axis 35B. Referring again toFIG. 4, in step 2 the ablation laser is activated and the ablation laserbeam travels along an optical axis 13, reflecting off the turning mirror17, and emitting from the hand piece 4 along the optical axis 18. Thelaser beam may ablate a portion of the tooth 28 within an area oftreatment according to the pattern 30.

Step 3 shows the sensor 22A imaging the surface of the tooth 28 afterthe ablation in step 2. In step 3, the laser beam is turned off. Steps 4and 6 illustrate that the ablation laser is reactivated and, as such,the ablation region 30 can get larger. In step 5, the laser beam isturned off and a measurement is obtained after the ablation in step 4.This treatment process including alternating measurement and ablationsteps can continue until a selected treatment is completed.

One advantage of the on-axis imaging system is that the operator canalign the system for imaging and measurement, and can then easily switchover to laser ablation without moving the hand piece. Various embodimentof a 3D measurement/scanning system may include an imaging device suchas a CMOS chip, coupled to a lens stack that is mounted to a motorshaft, so that a short depth of focus can be achieved. The motor mayinclude both a controller and amplifier, and the lens stack motorcontrol can be linked to the system processor. By controlling the lensstack motor position through a central control system, the image can befocused, or moved automatically or remotely using a hand joystick or thefoot pedal, or another input device. A foot pedal is illustrative only;the control of any parameter described below can be achieved using anysuitable input device such as a mouse, keyboard, joy stick, touch screenpanel, a slider switch, etc.

The motor and lens stack allow for the shortest depth of focus positionof the image sensor to be adjusted as the tooth ablation continues sothat a number of image slices, e.g., images at gradually increasingdepths, can be captured. Once the images are obtained, a digital fileincluding those images can be processed using hardware and/or softwarecomponents so as to determine the portion of the captured images that isin focus. Based on such determination, a depth of each slice can bedetermined, and a contour of the dental treatment region for each imageslice can be computed using the corresponding depth. Depth determinationcan also account for any unintentional movement of the hand piece, suchas jitter.

FIG. 5 shows an exemplary treatment process including alternatingscanning (i.e., contour determination) and ablation steps, and thecreation of a final restoration digital model. Specifically, step 1depicts an untreated tooth. Step 2 illustrates four iterations of thealternating procedure. In each iteration, a substantiallytwo-dimensional (2D) image measurement, i.e., contour determination ofthe tooth, is followed by ablation. As the tooth is ablated, the 2Dimage slices and the corresponding contours 502-508 that are determinedby analyzing the captured images are digitally stored. As these slicesrepresent ablated tissue, they are not actually present on the toothafter the ablation.

Step 3 illustrates a total of eight substantially 2D image slices502-516, and step 4 illustrates twelve substantially 2D image slices502-524. Step 5 illustrates that the twelve digital 2D image slices502-524 obtained from steps 2-4 can be digitally combined to create asolid 3D representation (e.g., as a digital image) of the tissue thatwas ablated and needs to be replaced, as depicted in step 6. It shouldbe understood that a restoration that includes 12 scans is illustrativeonly and, in general, a restoration can include fewer (e.g., 2, 3, 4,etc.) or many more (e.g., 50, 100, 200 etc.) scans.

One advantage of the various embodiments of the integrated scanning andablation system is that the restoration can be more accurate and is morelikely to resemble the original tooth, relative to conventionaltechniques. This is because in conventional techniques, images aretypically taken before and after the treatment only, because takingadditional images during the treatment can be cumbersome and/orpotentially harmful to a person being treated, as the operator wouldneed to frequently switch between the ablation and scanning systems.Moreover, conventional scanning and laser-based ablation systems cannotbe readily integrated, because these systems include optical subsystemsthat are generally incompatible with each other.

In some embodiments described herein, optical subsystems of the ablationsystem, such as the galvo-controlled mirrors, are adapted for scanningas well. Additionally, or in the alternative, the scanning and ablationsystems may use different optical components, such as separate turningmirrors 17, 26 (shown in FIG. 2A). In various embodiments, theparticular geometries of these components, such as their positions,relative angles, etc., are used in analyzing the scanned images so as todetermine contours of the treated region. This can enable obtaining anumber of intermediate slices (e.g., 10, 50, 100, or more) during thetreatment in addition to the images captured before and after thetreatment, without having to swap in and out the scanning andablation/treatment systems. The depth of two consecutive slices can besmall (e.g., 0.02 mm, 0.05 mm, 0.1 mm, 0.5 mm, etc.), relative to thetotal depth of a cut during a treatment, which can be up to about 1 cmor even more. A contour at each slice can be a substantiallytwo-dimensional contour, and a 3D image can be constructed using the 2Dcontours, as depicted in steps 5 and 6 of FIG. 5.

As the slices obtained during treatment correspond to small changes indepth (i.e., the distance between two consecutively imaged surfaces)relative to the change in depth associated with the images before andafter the treatment, in various embodiments described herein only asmall degree of interpolation is necessary to determine the shape of theremoved tissue from one imaged contour to the next imaged contour. Thiscan simplify the processing and/or increase accuracy thereof. Moreover,the images can be obtained while a single hand piece, facilitating bothtreatment and imaging, is held in a patient's mouth. Therefore, theinaccuracies related to a lack of orientation information and referencecan be avoided or mitigated.

In some embodiments, the processor generating the 3D model using the 2Dcontours determines the depths of the slices corresponding to thosecontours by analyzing some or all of the contours and/or some or all ofthe images corresponding to those contours. This analysis can compensatefor any unintentional movement of the hand piece (e.g., jitter) duringtreatment and/or scanning. Based on the parameters set by the operator,the main system computer/processor can estimate the depth of cut fromeach treatment step. As the 2D contours are determined from tissue scansthat are interleaved between different treatment steps, the processormay use the estimated depths of one or more of the previously performedtreatment steps in accurately determining the 2D contour of an imageobtained in a particular scan. The processor may also use the estimateddepths in the reconstruction of the 3D model, thereby increasing theaccuracy thereof.

In various embodiments, using the user interface 5 (depicted in FIG. 1),a wide array of hard and soft tissue procedures can be employed. By wayof example and without limitation, an operator may insert the hand piece4 into the patient's mouth and observe the image of the hard or softtissue on the user interface 5 or another monitor. While viewing thetooth, the hand piece 4 may be specifically positioned to view an areaof interest, such as an area to be treated. The laser beam guidancesystem can be used to scan the dental treatment area according to apattern of light and/or may be used to guide the laser beam duringtreatment. Using the contours generated during alternating scanning andtreatment steps, a three dimensional (3D) model of portions of thetissue removed from the dental treatment area can be created. Based onthe 3D model, a restoration can be created and applied to the treateddental area. Optionally, the 3D model can be modified prior to creatingthe restoration. The modification can be beneficial if the portion ofthe tissue removed included defects such as a lost part, e.g., due to achipped tooth, or was deficient in any respect. These defects anddeficiencies can be eliminated or reduced using the optionalmodification. Any of a variety of 3D modeling tools and systems can beemployed, including haptic-based interactive modeling systems to modifythe model, prior to manufacture of the replacement piece or restoration.

While the invention has been particularly shown and described withreference to specific embodiments, it will be understood by thoseskilled in the art that various changes in form and detail may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims. The scope of the invention is thusindicated by the appended claims and all changes that come within themeaning and range of equivalency of the claims are therefore intended tobe embraced.

What is claimed is:
 1. A device for determining a contour of a dentaltreatment area, the device comprising: a laser beam guidance system forguiding, via a handpiece, a laser beam to a dental treatment area; animaging system to obtain an image of the dental treatment area based onlight rays reflected therefrom and traveling via the hand piece; and acomputation system adapted for determining, based on the image obtainedby the imaging system, a contour of a surface of the dental treatmentarea.
 2. The device of claim 1, wherein the imaging system comprises anadjustable focus lens.
 3. The device of claim 2, further comprising atleast one of a joystick and a foot pedal for adjusting a focal length ofthe adjustable focus lens.
 4. The device of claim 2, wherein theadjustable focus lens comprises at least one of a motorized lens stackand a liquid lens.
 5. The device of claim 1, wherein the computationsystem is adapted for determining an in-focus portion of the image. 6.The device of claim 1, wherein the computation system is adapted fordetermining the contour based at least in part on a geometry of at leastone of a component of the laser beam guidance system and the imagingsystem.
 7. The device of claim 1, wherein both the laser beam and thelight rays reflected from the dental treatment area travel along acommon optical axis.
 8. The device of claim 7, further comprising asplitter for directing the light rays reflected from the dentaltreatment area to the imaging system.
 9. The device of claim 1, whereinthe imaging system is located within the handpiece.
 10. (canceled) 11.The system of claim 1, further comprising an illumination system forproviding light to the dental treatment area.
 12. The system of claim11, wherein the illumination system is adapted for providing lighthaving a pattern.
 13. The system of claim 12, wherein the patterncomprises at least one of a spot, a one-dimensional pattern, and atwo-dimensional pattern.
 14. The system of claim 11, wherein the laserbeam guidance system is adapted to scan the dental treatment area bydirecting light from the illumination system.
 15. A method ofdetermining a contour of a dental treatment area, the method comprisingthe steps of: (a) receiving at an imaging system a first image based ona first set of light rays reflected from a dental treatment area andtraveling via a handpiece; (b) generating a first contour of the dentaltreatment area based on the first image; (c) directing via the handpiecea laser beam to the dental treatment area using a laser beam guidancesystem, to remove at least a portion of tissue from the dental treatmentarea; (d) receiving at the imaging system a second image based on asecond set of light rays reflected from the dental treatment area andtraveling via the handpiece; (e) generating a second contour of thedental treatment area based on the second image; and (f) repeating steps(c) through (e) until treatment is completed.
 16. The method of claim15, wherein at least one of the first contour and the second contour isa two-dimensional (2D) contour.
 17. The method of claim 15, wherein:receiving the first image comprises adjusting a focal length associatedwith the imaging system; and generating the first contour comprisesdetermining an in-focus portion of the first image.
 18. The method ofclaim 15, wherein the focal length is adjusted using at least one of ajoy stick and a foot pedal.
 19. The method of claim 15, wherein both thelaser beam and the first and second sets of light rays reflected fromthe dental treatment area and received by the imaging system travelalong a common optical axis.
 20. The method of claim 15, whereinreceiving the first image comprises scanning the dental treatment areaaccording to a pattern of light obtained from an illumination system.21. The method of claim 20, wherein the laser beam is guided to thedental treatment area along a first axis and the first and second setsof light rays reflected from the dental treatment area and received bythe imaging system travel along a second axis that is at an angle withrespect to the first axis. 22.-27. (canceled)